1. Field of the Invention
The present invention relates to a LAN (Local Area Network) type internet access network and a subscriber line accommodation method for use in the same network.
2. Description of Related Art
In a conventional LAN type internet access network, a subscriber line accommodation method such as shown in FIG. 8 is used. As shown in FIG. 8, the conventional LAN type internet access network is constructed with L2 (Layer 2) switch 11 accommodating subscriber lines, DHCP (Dynamic Host Configuration Protocol) server 12 and service/management device 13 connected to an internet.
DHCP server 12 uses a MAC (Media Access Control) address of a user terminal (not shown) connected to a subscriber line as a key to assign an IP (Internet Protocol) address to the user terminal when the IP address is already assigned to the user terminal or to assign a new IP address to the user terminal and return the new IP address thereto when an IP address is not assigned to the user terminal. First, a user terminal, after the user terminal is connected to a subscriber line, transmits a DHCP request to receive an assignment of IP address. The DHCP request is transmitted by broadcast.
In general, any node in a LAN, which performs an IP communication with another node within the same LAN, acquires a MAC address of the associated another node by using an IP address of the associated node as a key and assembles a transmission packet on the basis of the MAC address. In this case, an ARP (Address Resolution Protocol) is a protocol for inquiring the MAC address corresponding to the IP address and the ARP request is transmitted by broadcast.
The L2 switch shown in FIG. 8 accommodates a plurality of subscriber lines and is connected to an upper side of the internet, which includes service/management device 13, to exchange data packets. Service/management device 13 includes a group of such devices as a default gateway for IP connection to the internet and a server or a router for providing various IP services including a WWW (World Wide Web) service to user terminals.
However, when the broadcast is inhibited by the L2 switch in the subscriber line accommodation method for the conventional LAN type internet access network, which is mentioned above, a transmission of the ARP request between user terminals in the subscriber lines becomes impossible. Therefore, there is a problem that IP communication between user terminals accommodated in the subscriber line is impossible.
Further, when the broadcast is allowed by the L2 switch in the conventional subscriber line accommodation method, the DHCP request and ARP request are transmitted to user terminals by broadcast. Therefore, there is another problem that it is impossible to systematically prohibit unintentional common possession of resources by user terminals or to prevent leakage of a MAC address of a user terminal accommodated in a subscriber line to a third party accommodated in another subscriber line in the same system.